Spyder3 SG-34 GigE Vision Color Manual 41
Teledyne DALSA 03-032-20124-00
Camera Calibration
Processing Chain Overview and Description
The follow ing d iagram show s a simp lified block d iagram of the camera’s digital p rocessing chain.
The digital processing chain contains the FPN correction, the PRNU correction, the background subtract,
and the digital gain and offset adjustments.
These elements are user programmable and most are members of the Analog Controls and Advance
Processing sets.
Figure 23: Signal Processing Chain
Digital Processing
1. Fixed pattern noise (FPN) calibration (calculated using the FPN Calibrate parameter) is used to
subtract away individual pixel dark current.
2. Photo-Response Non-Uniformity (PRNU) coefficients (calculated using the PRNU Target and
Calibrate PRNU parameters in the Advance Processing family) are used to correct the difference in
responsivity of individual pixels (i.e. given the same amount of light different pixels will charge up
at different rates) and the change in light intensity across the image either because of the light source
or due to optical aberrations (e.g. there may be more light in the center of the image). PRNU
coefficients are multipliers and are defined to be of a value greater than or equal to 1. This ensures
that all pixels will saturate together.
3. Calibrate White Balance calibrates individual colour gain settings so that the outputs are equal
between the colors.
4. The Color Gain (DB) specifies the gain in dB for a given color and tap.
5. Background subtract (Background Subtract (DN) parameter) and system (digital) gain (Digital
Gain (DN) parameter) are used to increase image contrast after FPN and PRNU calibration. It is
useful for systems that process 8-bit d ata but want to take ad vantage of the cam era’s 12 bit d igital
processing chain. For example, if you find that your image is consistently between 128 and 255DN (8
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